Method and device for forming a winding on a non-planar substrate

ABSTRACT

The electronic device ( 10 ) comprises a capacitor ( 12 ) and an inductor ( 11 ) and is present on a substrate ( 1 ) with an unplanarized surface ( 2 ). This is realized in winding ( 21 ) of the inductor ( 11 ) has a thickness of at least 1 micron and has a planarized upper surface ( 81 ). The upper electrode ( 32 ) of the capacitor is present in a second electrode layer ( 6 ) and has a lower surface ( 82 ) which is spaced from the substrate ( 1 ) by a larger distance than the upper surface ( 81 ) of the lower electrode ( 31 ). The second electrode layer ( 6 ) preferably includes a second winding ( 22 ) of the inductor ( 11 ). The electronic device ( 10 ) is suitable for use at high frequencies.

The invention relates to a method of manufacturing an electronic devicecomprising a substrate with on a surface thereof a capacitor and aninductive element, which capacitor includes a first electrode and asecond electrode and an intermediate dielectric, and which inductiveelement comprises a first winding.

The invention also relates to an electronic device comprising acapacitor and an inductive element, which capacitor includes a firstelectrode and a second electrode and an intermediate dielectric andwhich inductive element comprises a first winding, which devicecomprises a substrate on a surface thereof are present:

-   -   a first metal film, in which the first winding of said inductive        element and the first electrode of the capacitor are defined;    -   a second metal film comprising the second electrode of the        capacitor;    -   a dielectric film of a dielectric material, part of which is the        dielectric.

The invention further relates to a multilayer substrate with internalconductors provided with a measurement structure for measurement of adielectric constant of a dielectric.

The invention further relates to a method of testing an electronicdevice comprising an insulating body with internal conductors and layersof dielectric material, the device being designed to operate atfrequencies of more than 100 MHz, which method including thedetermination of a dielectric property of a layer of dielectric materialwith a measurement structure.

Such a device is known from WO-A-97/16836. The known device is atransformer which has been manufactured by means of thin filmtechnology. The second metal film, which is deposited directly on theplanarized surface of the substrate, comprises gold and has a thicknessof less than 100 nm. Defined in the second metal film are the firstelectrode of the capacitor, bond pads and interconnects, whichinterconnects intersect the coupled inductor. The first metal film ofthe known device comprises copper and has a thickness of 2–5 micron.This renders the device suitable for use at high frequencies in themicrowave and rf range. The device furthermore comprises a third metalfilm, which likewise comprises copper and has a thickness of 2–5 micron.Said third metal film is separated from the first metal film by aseparation layer. Said separation layer comprises an organic materialhaving a low dielectric constant and has a thickness of 2–30 micron.Because of the low dielectric constant and the great thickness of theseparation layer, the capacitive coupling between the first and thesecond element of the coupled inductor in the known device is onlysmall, even at high frequencies. This renders the known device suitablefor use in RF applications, in particular as a balanced-to-unbalancedtransformer, also known as a balun transformer.

It is a drawback of the known device that the substrate must have aplanarized surface. If such is not the case, premature failure ofthe—thin film—capacitor will occur upon application of an electricfield.

Thus it is a first object of the invention to provide a method ofmanufacturing an electronic device of the kind mentioned in theintroduction, which is suitable for use in RF applications, and in whichplanarisation of the substrate is not necessary.

It is a second object of the invention to provide a device of the kindreferred to in the introduction, which is suitable for use in RFapplications and for which the substrate can be chosen freely, since nosubstrate planarisation is required.

The first object is achieved in that the method comprises the steps of:

providing a first metal film on the surface of the substrate, in whichfirst metal film are defined the first electrode of the capacitor andthe first winding of the inductive element;

providing a dielectric film of dielectric material on the first metalfilm;

providing a separation layer of dielectric material on the dielectricfilm in a desired pattern, such that the separation layer covers thefirst winding and that a perpendicular projection of the separationlayer on the first metal film falls partially within the firstelectrode; and

providing a second metal film on the dielectric film and the separationlayer, in which second metal film is defined the second electrode of thecapacitor.

Because both the first electrode and the first winding are defined inthe first metal film on the substrate surface, the first metal film willhave a substantial thickness, hence it was found that no planarisationof the substrate is necessary. The thickness however may lead to anon-uniformess of the capacitor, particularly since an interconnectiontrack interconnecting the second electrode will be present next to thefirst capacitor electrode. This would lead to a so-termed “stepcoverage”. Such non-uniformess is prevented in the provision of theseparation layer.

In a suitable embodiment, the first and second metal film are providedby applying a seed layer and growing the film to a desired thicknesswith electroplating. The use of electroplating has the advantage that itis a technique that can be well integrated with IC processing, such asdamascene and dual-damascene. Further on, the thicknesses larger than 1micron, preferably 3 to 8 micron, are well achievable. Besides, even ifthe seed layer does not coat the underlying surface completely, theresulting electroplating step will result in the metal film as desired.

In a further embodiment a brightener is added to the electrochemicalbatch used for the electroplating. It has turned out that the resultingmetal film, when comprising said brightener, is also capable ofsmoothening substrates that exhibit a high degree of roughness. A highdegree of roughness is characterized by, for example, a variation of thesurface in the direction perpendicular to the stack of layers—thez-direction—of 3 micron or more. An additional advantage of the use of abrightener is that the bath can be operated at higher current values,which accelerates the deposition of metal, particularly copper.

Advantageous examples of substrates exhibiting a high degree ofroughness are sintered ceramic substrates, such as alumina, AIN andLow-Temperature Cofired Ceramic—or LTCC—substrates. Such substrates havedistinct advantages over substrates of for example, silicon or glass:the electric losses which occur at high frequencies are lower than theelectric losses of silicon substrates; the thermal conduction is betterthan that of glass substrates, and in addition, said substrates arecheaper.

It will be understood that further embodiments are possible.Particularly with copper as material of the metal films, it is suitableto provide barrier layers. Also, an additional separation layer, to beapplied before the first metal film, may be present between the patternsin the first metal film, and result in a planarized surface of thislayer and the first metal film. Also, the metal films, the dielectricfilm and the separation layer may be part of a multilayer stack, thatcan be used as a substrate on its own. Further on, additional elementsmay be provided into the first and second metal films, so as to improvethe quality, and make interconnects.

The second object to provide a device of the kind referred to in theintroduction is achieved in that:

the first metal film is present between the surface of the substrate andthe dielectric film and has a thickness that is larger than apenetration depth at a minimal operation frequency;

a patterned separation layer of a dielectric material is present betweenthe first and the second metal film, which separation layer has asmaller capacitance density than the dielectric film, and

a perpendicular projection of the separation layer on the first metalfilm falls partially within the first electrode of the capacitor.

Due to the thick layer—preferably of copper—, it is not necessary toprovide at least one of the electrodes of the capacitor in a separatelyapplied, thin layer, on a planarized substrate. Instead thereof, thecapacitor electrodes are applied in the same metal films as otherelements, such as windings of inductive elements, interconnect tracks,vertical interconnect areas, transmission lines and the like. An optimumthickness of the metal film is a thickness of about twice thepenetration depth. At such a thickness the current that penetrates up tothe penetration depth, is the least disturbed, while the couplingbetween tracks within the same film is minimal. And the higher thecurrent, the higher the Q-factor of the inductor and the lower theEquivalent Series Resistance, briefly ESR, of the capacitor. At anoperating frequency of 1 GHz, said penetration depth is 2–3 micron,depending on the metal used in the metal film. At 10 GHz, saidpenetration depth is less than 1 micron.

Besides, due to the patterning of the separation layer and thedielectric film, the coupling between the first and the second metalfilm can be tuned to desire: either direct contact—neither separationlayer, nor dielectric film—or capacitive coupling—only dielectricfilm—or only inductive coupling—separation layer with or withoutdielectric film.

Since no additional thin layer is necessary for a capacitor electrode,the device of the invention may well be a multilayer structure withcopper layers, such as a multilayer interconnect structure of anintegrated circuit and a multilayer structure of a multilayer substrateof ceramic or resin material.

It is preferred that the capacitance density of the separation layer isat least ten times lower than that of the dielectric film. Saidcapacitance density, which is also known by the term dielectricthickness, equals the ratio between the dielectric constant and thethickness of the layer of dielectric material. Preferably, theseparation layer has a capacitance density of less than 30 pF/mm², morepreferably less than 10 pF/mm² and even more preferably less than 3pF/mm². A capacitance density of 3 pF/mm² can be realized by depositinga low-K material in a thickness of 8 micron or more. Examples of low-Kmaterials are, for example, benzocyclobutene, polyimide, porous silicaand silsesquioxane. Preferably, the dielectric film has a capacitancedensity of more than 80 pF/mM², more preferably more than 150 pF/mm². Acapacitance density of 150 pF/mm² can inter alia be realized by usingSiN_(x) in a thickness of about 0.4 micron as the dielectric material.

In a first embodiment, the inductive element comprises a second winding,that is present in the second metal film and separated from the firstwinding through the separation layer. Through the use of an inductiveelement with more than one winding, the surfacial area of the inductiveelement can be substantially reduced. Further on, the first and thesecond winding need not to be interconnected, but form the first and thesecond coils of a transformer. The separation layer determines thedistance between the first and the second winding, therewith minimizingundesired capacitive coupling and maximizing inductive coupling.

The inductive element of this first embodiment is for instance a coupledinductor, which preferably forms part of a balun transformer. Suchtransformers may have a resonance frequency of about 2–2.4 GHz, whichrenders them suitable for use in according with varioustelecommunication protocols, such as Bluetooth, W-LAN, W-CDMA and thelike.

The inductive element can be an coil as well. The first and the secondwinding are interconnected in that case. Preferably, a third and afourth winding are present in, respectively, the first and the secondmetal film. With such an inductive element, inductance values of 25–35nH can be realized on a surface area of 1 mm², and the Q-factor is 30 ormore. Apart from a coil having a large inductance, the inductive elementmay alternatively be a coil having a relatively small surface area. Thesurface area of the coil comprising two windings in two metal films hasbeen reduced by 50% in comparison with a coil comprising one or morewindings in only one metal film.

In a further embodiment, the dielectric material of the separation layeris air. In this way, inductors comprising an air gap are obtained. Airhas the advantage of having a very low dielectric constant of 1. Thecapacitance between the first and the second winding of the inductiveelement is very small in that case. This embodiment can be realized bydepositing a soluble material such as a photoresist in a desiredthickness as the separation layer. After application and patterning ofthe second metal film, said material can be dissolved in a solvent whichdoes not affect the dielectric material of the dielectric film. Spacersof a third material, for instance silicon oxide, can be provided tosupport the second metal film as far as necessary.

In another embodiment, which is particularly preferred in combinationwith the embodiment with an inductive element comprising a first and asecond winding, the substrate comprises a layer of semiconductormaterial wherein a plurality of semiconductor elements are defined thatare interconnected so as to form an integrated circuit. This impliesthat the inductive element and the capacitor are part of theinterconnect structure of the integrated circuit. The device of theinvention is very suitable therefor. First of all, its manufacture iscompatible, since the only metal layers that are present are metallayers of standard available materials, such as copper, and also thedielectric layers are of material that is known in semiconductorprocessing. Secondly, it uses only a limited number of layers, that canbe used for interconnection purposes as well. The interconnectstructure, that usually comprises 4–6 metal layers, does not need to beextended to a larger number of layers. Thirdly, the lateral dimensionsof the structure is relatively limited, so that it fits into thesurfacial area of the integrated circuit and lets space left forinterconnects.

In yet another embodiment, a micro-electromechanical component—alsoknown as MEMS components—is present. To that end, the device comprises afirst MEMS electrode and a second MEMS electrode, the first and thesecond MEMS electrode being present in, respectively, the first and thesecond metal film. The first and the second MEMS electrode are separatedfrom each other by the separation layer and a layer of air.Alternatively, the separation layer maybe of air. Microelectromechanicalcomponents may be used at various places in the front end of a mobiletelephone, inter alia as a switch, a resonator, a filter and anadjustable capacitor. More in particular a MEMS component may be usedfor adjusting the output impedance of an impedance matching circuit andfor adjusting the resonance frequency of a voltage controlledoscillator. (VCO) tank circuit.

In again another, but very suitable embodiment, the capacitor and theinductive element are part of a measurement structure, wherein the firstwinding of the inductive element interconnects the first and the secondelectrode of the capacitor, and the measurement structure furthercomprises a first and a second transmission line, which lines aredefined in the second metal film, are located substantially parallel toeach other and perpendicular projections of the lines on the first metalfilm overlap with the first winding.

In the resonant structure of inductor and capacitor a small signal isprovided by inductive and capacitive coupling from one of thetransmission lines. The amount of coupling therein is so small that theLC-structure is hardly influenced. The transmission of this signal tothe second transmission line is measured as a function of the frequency.At the resonance frequency a strong transmission takes place. It hasbeen found that the position of this resonance is influenced by thecapacitor. Such could be expected at low frequencies, but is unexpectedfor RF applications. By comparison with a reference value, the qualityof the capacitor can be controlled. Such is particularly important formultilayer substrates.

The measurement structure in the device of the invention hasconsiderable advantages over known measurement structures for themeasurement of the dielectric constant. First of all, the size of thestructure is considerably reduced. In comparison with a ring-shapedresonator the necessary surface area is reduced 50 times at 1.8 GHz, 20times at 2.4 GHz and about 6 times at 4.5 GHz. Secondly, the dielectricconstant can be obtained without any information on the layers aroundthe capacitor.

The invention also relates to a multilayer substrate with internalconductors provided with a measurement structure for measurement of adielectric constant of a dielectric.

The invention further relates to a method of testing an electronicdevice comprising an insulating body with internal conductors and layersof dielectric material, the device being designed to operate atfrequencies of more than 100 MHz, which method including thedetermination of a dielectric constant of a layer of dielectric materialwith a measurement structure.

Such a method and such a multilayer substrate are for instance knownfrom D. I. Amey & S. J. Horowitz, “Test Characterise High FrequencyMaterial Properties”, Microwave & RF, August 97, and also “MicrowaveMaterial Characterisation”, Proc. Int. Symposium on Microelectronics(ISHM) 1996, 494–499.

In the known method use is made of stripline, T- and ringresonators asmeasurement structures, particularly for frequencies above 1 GHz. Suchresonators are provided with special metallizations on the dielectriclayer to be measured. The result thereof is the magnitude of atransferred signal from entrance to exit of the measurement structure.

It is a disadvantage of the known structure, that the electrical fieldis spreaded over all layers of a multilayer substrate. The position ofthe resonance frequency and the width of the resonance curve depend onthe thickness and the type of layers of all layers in the multilayerstack. When measuring, it is therefor necessary to calculate first theenvironmental contribution, also called the effective dielectricconstant. Only thereafter, the relation between this effectivedielectric constant and the real structure can be found out, which isquite complicated.

It is therefore a third object of the invention to provide a multilayersubstrate of the type referred to in the introduction, with an improvedmeasurement structure.

It is a fourth object of the invention to provide a measurement methodthat is less complicated and provides direct results.

The third object is realized in that it comprises:

a capacitor having a first and a second electrode and the intermediatedielectric,

an inductive element having a first winding, wherein the first windinginterconnects the first and the second electrode of the capacitor;

-   -   a first and a second transmission line, which lines are located        parallel to each other and are capacitively and inductively        coupled to the first winding of the inductive element.

In the resonant structure of inductor and capacitor a small signal isprovided by inductive and capacitive coupling from one of thetransmission lines. The amount of coupling therein is so small that theLC-structure is hardly influenced. The transmission of this signal tothe second transmission line is measured as a function of the frequency.At the resonance frequency a strong transmission takes place. It hasbeen found that the position of this resonance is influenced by thecapacitor. Such could be expected at low frequencies, but is unexpectedfor RF applications. By comparison with a reference value, the qualityof the capacitor can be controlled. Such is particularly important formultilayer substrates.

The measurement structure in the device of the invention hasconsiderable advantages over known measurement structures for themeasurement of the dielectric constant or other dielectric properties.First of all, the size of the structure is considerably reduced. Incomparison with a ring-shaped resonator the necessary surface area isreduced 50 times at 1.8 GHz, 20 times at 2.4 GHz and about 6 times at4.5 GHz. Whereas ring-resonators have a diameter in the order ofcentimeters, the structure of the invention can be will provided on ansurface area of about 0.3*0.3 cm, more or less frequency independent.Secondly, the dielectric constant can be obtained without anyinformation on the layers around the capacitor. Th electric field is inthis case only present between the capacitor electrodes.

Preferably the substrate is provided with a first and a second metalfilm, the first metal film comprising the first electrode of thecapacitor and the first winding of the inductive element, the secondmetal film comprising the second electrode of the capacitor and thetransmission lines, the first and second metal film being mutuallyseparated through a dielectric film of dielectric material constitutingthe dielectric of the capacitor and a separation layer of dielectricmaterial being at least present between the first winding of theinductive element and the transmission lines. This structure has beenfound to be very well applicable for this object. In a furtherembodiment, a perpendicular projection of the separation layer on thefirst metal film falls partially within the first electrode of thecapacitor.

The fourth object is achieved in that the device or the multilayersubstrate according to the invention is tested and its measurementstructure is used to measure the resonance frequency, which is comparedto a reference value and converted to a desired quantity, such as thedielectric constant or the dielectric loss. Under the conditions thatsurface area of the capacitor and inductance are the same in bothreference and measurement, the conversion of resonance frequency f_(res)to dielectric constant ε or dielectric thickness ε/d is done with:(ε/d)_(device)=(ε/d)_(reference) (f_(res, reference)/f_(res, device))².Herein, the subscript reference indicates the reference value and thesubscript device indicates the value of the sample that is actuallymeasured. Data on the dielectric loss (ordinarily expressed as tan δ)can be obtained from the resonance frequency and the resonance widthΔf_(3 dB): tan δ=(Δf_(3 dB)/f_(res))_(device)—(1/Q)_(metal, reference),wherein the Q is Q-factor for the metal film of the reference. Furtherdetails and embodiments thereof will be clear to the skilled person.

These and other aspects of the method of manufacturing and theelectronic device will now be explained in more detail by means ofembodiments and drawings. The drawings are diagrammatic representations,not to scale, in which like numerals indicate like parts. In thedrawings:

FIG. 1 is a diagrammatic sectional view of the device;

FIG. 2 shows a roughness profile of the non-planarized substrate;

FIG. 3 shows a roughness profile of the substrate coated with the firstmetal film;

FIGS. 4 a and 4 b are diagrammatic top plan views of the electrodelayers of one embodiment of the invention;

FIG. 5 shows an electric diagram equivalent to the embodiment of FIG. 4;

FIG. 6 is a diagrammatic sectional view of a second embodiment; and

FIG. 7 shows an electric diagram of the second embodiment.

The electronic device 10 which is shown in FIG. 1 comprises a substrate1 having a surface 2. The substrate 1 comprises alumina. Present on thesurface 2 is a first metal film 3, which comprises copper and which hasa thickness of 5 micron. FIG. 2 shows a roughness profile of thenon-planarized substrate 1. Both sectional views have been obtained bymeans of Atomic Force Microscopy. The length of the section is plottedon the x-axis. The height of the surface is plotted on the y-axis. Thefigures give an impression of the roughness of the substrate; it shouldbe noted that the scale of the x-axis is smaller than the scale of they-axis. The surface 2 of the non-planarized substrate 1 exhibitsvariations in height ranging between 500 and 1900 nm. The surface ispeaked, the peaks having a width in the order of 1–4 micron. Thegradient of the peaks is in the order of 400–800 nm per micron oflength. The surface of the first electrode layer 3 exhibits variationsin height ranging between 700 and 1650 nm. The surface slopes gradually,with a gradient in the order of 70 nm per micron. The extremes arespaced about 10 micron apart. Upon comparison of the two surfaces itappears that the first metal film 3 planarizes the surface 2 of thesubstrate 1.

As is shown in FIG. 1, the first metal film 3 is coated with adielectric film 4, which in this case comprises SiN_(x) having arelative dielectric constant of 6.5 and which has a thickness of 400 nm.Present on the dielectric film 4 is the separation layer 5, which inthis case comprises benzocyclobutene having a relative dielectricconstant of 2.7 and which has a thickness of 10 micron. Present on theseparation layer 5 is the second metal film 6, which comprises copperand which has a thickness of about 5 micron. The metal films 3,6, thedielectric film 4 and the separation layer 5 are all patterned inaccordance with a desired pattern, with an inductive element 11, acapacitor 12 and a via 13 being defined.

The inductive element 11 comprises a first portion 21 in the first metalfilm 3 and a second portion 22 in the second metal film 6. The first andthe second portion 21,22 are inductively coupled as a result of thesecond portion 22 substantially overlapping, and in this caseessentially coinciding with, the first portion 21 upon perpendicularprojection on the first metal film 3. There is no or at least nosignificant capacitive coupling between the first and the second portion21,22 of the inductive element 11, because of the presence of theseparation layer 5 between said portions. The dielectric film 4 is alsopresent, but its influence on the capacitance between the two portions21,22 is only small.

The capacitor 12 includes a first and a second capacitor electrode 31,32present in, respectively, the first and the second metal film 3,6. Adielectric 33 consisting of the dielectric film 4 is present between thelower and the upper electrode 31,32 of the capacitor 12. Part of thelower surface 82 of the upper electrode 32 is in contact with thedielectric film 4, and another part is in contact with the separationlayer 5. The lower surface 82 is positioned above the upper surface 81of the lower electrode 31 in its entirety.

The via 13 is formed at places where both the separation layer 5 and thedielectric film 4 have been removed by patterning.

Embodiment 1

The device that is shown in FIG. 1 is formed in the following way. Thesurface 2 of the substrate 1 is coated with a seed layer of copper in athickness of 200 nm by means of a sputtering technique. Then aphotoresist is deposited, exposed via a first mask and developed.Following this, copper is grown thereon by means of an electroplatingprocess. The device—insofar as it has been formed—is to that endimmersed in an aqueous bath containing Cu²⁺ ions, counter ions and abrightener. Copper is separated by means of a galvanic process. As aresult of the addition of the brightener, the grain size of the copperremains limited. As a result, a copper film having a smooth uppersurface is obtained.

After completion of the electroplating process and after the first metalfilm 3 has been formed in a desired pattern, the photoresist and theseed layer present under said photoresist are removed. The surface ofthe metal film 3 is cleaned. The dielectric film 4 of SiN_(x) isdeposited and patterned by means of a photoresist, exposure, etc. Thenthe separation layer 5 is spin-coated thereon. The separation layer is alayer of benzocyclobutene comprising a photosensitive component. Theseparation layer 5 is dried and, after exposure, developed in a mannerwhich is usual for benzocyclobutene. Since benzocyclobutene has aplanarizing effect, polishing is not necessary. Subsequently, the secondmetal film 6 is deposited in the same way as the first metal film 3.

The device 10 is now complete. If bond pads are desired, a film of Aumay be coated onto the second metal film 6. The presence of a barrierlayer between the second metal film 6 and the film of Au is notrequired.

Embodiment 2

The surface 2 of substrate 1 is coated with the first metal film 3 inthe manner described in embodiment 1. Then the device is placed in aplasma-enhanced chemical vapor deposition (PECVD) reactor. In saidreactor, an SiO₂ film is first deposited in a thickness of 200 nm via amask. This is done by depositing trimethyl silane and N₂O in aproportion of 1:20 or 1:30. Deposition rates range between 10 and 60sscm for the silane and between 200 and 1800 sscm for the N₂O. Thetemperature ranges between 150 and 400° C., the pressure between 2 and10 Torr and an RF power between 50 and 250 Watt is used. Subsequently,the mask is substituted with a second mask and the ratio between the twogas flows is changed into a ratio ranging between 1:3 to 1:7. Thisresults in an intermediate layer of methyl-doped SiO. Deposition ratesrange between 10 and 60 sscm for the silane and between 30 and 360 sscmfor the N₂O. Following this, a spin-on dielectric, such as methylsilsesquioxane (MSQ) or hydrogen silsesquioxane (HSQ) is deposited. MSQhas a relative dielectric constant of 2.9, and its empirical formula isCH₃SiO_(1.5). Since MSQ and PECVD-SiO₂ do not bond together very well,the MSQ not present on the intermediate layer can be removed.Subsequently, the second metal film is deposited in the manner describedin embodiment 1.

Embodiment 3

The surface 2 of substrate 1 is coated with the first metal film 3 andthe dielectric film 4 in the manner described in embodiment 1. Then alayer of an insulating material is deposited thereon and patterned, sothat only a few supporting structures remain. Subsequently, aphotoresist, such as HPR506, is spin-coated thereon in a thickness of 2micron. During said deposition, it is ensured that the upper sides ofthe supporting structures are level with the photoresist. Followingthat, the second is metal film 6 is deposited and patterned. Then thephotoresist is removed by placing the device in an acetone bath.

Embodiment 4

FIG. 4 shows an embodiment of the electronic device 10 according to theinvention. FIG. 5 shows the electrical equivalent of FIG. 4. FIG. 4 ashows the first electrode film 3. FIG. 4 b shows the second electrodefilm 6. The embodiment as shown is a balun. Said balun includes theinductive element 11 and a capacitor 12. Furthermore, a grounded pattern15 is present, as well as gates 41, 42, 43, 44. The second winding 22 ofinductive element 11 is connected to the grounded pattern 15 via gate44. The grounded pattern 15 is largely contained within the second metalfilm 6. At the gates 41, 42, 43, however, the pattern 15 is containedwithin the first metal film 3. Vias 13 provide the interconnectionbetween the parts of the pattern 15. The first winding 21 of inductiveelement 11 is connected to the upper electrode 32 of the capacitor 12 ata first end 23. The first winding of inductive element 11 is connectedto the lower electrode 31 of the capacitor 12 at a second 24. The gate42 is connected to the lower electrode 31 of the capacitor 12 by meansof via 46. A substantial overlap with the first winding 21 occurs uponperpendicular projection of the second winding 22 of the inductiveelement 11 on the first metal film 3. The measuring results that havebeen obtained are shown in table 1.

TABLE 1 Measured resonance frequency F_(res), insertion loss IL(measured on single and back-to-back baluns), difference in phase at theresonance frequency of the baluns for various inductor areas and linewidths. Difference line Width IL @ F_(res) (dB) of phase at No. Area(mm²) (μm) F_(res) (GHz) single/b.t.b. F_(res) (Deg) 1 0.5 × 0.5  25 2.21.1–1.3/1.2 183 2  50 2.2    0.7/0.7 183 3 100 2.3 0.5–0.6/0.6 183 40.75 × 0.75  25 2.3 1.0–1.3/1.1 173 5  50 2.1 0.7–0.8/0.6 183 6 100 2.2   0.5/0.4 182 7 1.0 × 1.0  25 2.3 1.3–1.8/1.5 185 8  50 2.1 0.6–0.8/0.6184 9 100 2.2 0.5–0.6/0.3 183 10     100 (*) 2.3    0.2/0.3 179 Themeasurement indicated (*) comprises 50 Ω SMD contacts rather than 50 ΩRF probes.

Embodiment 5

FIG. 6 shows a second embodiment of the device 10 according to theinvention. In this case, the dielectric material is preferably a siliconoxide SiO_(x), which has been deposited in a thickness of 1.0 micron bymeans of plasma-enhanced chemical vapour depostion. Prior to thedeposition of the separation layer 5, supporting structures 25 areformed from a photoresist material, such as HPR506. Then a secondelectrode film 6 of Al is deposited. Said film is coated with aphotoresist, which is developed in accordance with the desired pattern.Besides the upper electrodes 32 of the capacitor 12 and the secondwinding 22 of the inductive element 11, also access holes 26 are definedin this manner. The Al is removed by dry etching in a chlorine plasma.Then the photoresist is removed. Following this, the silicon oxide isremoved by means of an etchant comprising NH₄F, acetic acid, ethyleneglycol and water. This is followed by rinsing with H₂O and drying withisopropanol.

The result is a device comprising an inductive element 11, a thin filmcapacitor 12, vias 13 and a micro-electromechanical (MEMS) element 18.The MEMS element 18 comprises a first MEMS electrode 38 in the firstmetal film 3 and a second MEMS electrode 39 in the second metal film 6.Present between the MEMS electrodes 38,39 are the dielectric film 4 anda layer of air. The MEMS element 18 is stabilized by the vias 13.

FIG. 7 shows an electric diagram of the device according to theinvention incorporating the MEMS element 18. In this case, the device 50is an RF front end comprising a power amplifier 55, thin film capacitors12, inductive elements 11 and an antenna 56. The MEMS element forms partof the impedance matching circuit 57. The MEMS element 18 enablesadjustment of the output impedance in this application.

1. An electronic device (10,50) comprising a capacitor (12) and aninductive element (11), which capacitor (12) includes a first electrode(31) and a second electrode (32) and an intermediate dielectric (33),and which inductive element (11) comprises a first winding (21), whichdevice (10,50) comprises a substrate (1), on a surface (2) of whichthere are present: a first metal film (3), in which the first winding(21) of said inductive element (11) and the first electrode (31) of thecapacitor (12) are defined; a second metal film (6) comprising thesecond electrode (32) of the capacitor (12); a dielectric film (4) of adielectric material, part of which is the dielectric (33), characterizedin that: the first metal film (3) is present between the surface (2) ofthe substrate and the dielectric film (4) and has a thickness that islarger than a penetration depth at a minimal operation frequency; apatterned separation layer (5) of a dielectric material is presentbetween the first and the second metal film (3,6), which separationlayer (5) has a smaller capacitance density than the dielectric film(4), and a perpendicular projection of the separation layer (5) on thefirst metal film (3) falls partially within the first electrode (31) ofthe capacitor (12).
 2. An electronic device (10,50) as claimed in claim1, characterized in that the inductive element (11) comprises a secondwinding (22), that is present in the second metal film (6) and separatedfrom the first winding (21) through the separation layer (5).
 3. Anelectronic device (10,50) as claimed in claim 1, characterized in thatthe substrate (1) comprises a layer of semiconductor material wherein aplurality of semiconductor elements are defined that are interconnectedso as to form an integrated circuit.
 4. An electronic device (50) asclaimed in claim 1, characterized in that a microelectromechanicalcomponent (18) comprising a first MEMS electrode (38) and a second MEMSelectrode (39) is present, said first and said second MEMS electrode(38,39) being present in, respectively, the first and the second metalfilm (3,6), and the dielectric layer (4) and a layer of air beingpresent between the first and the second MEMS electrode (38,39).
 5. Anelectronic device (10) as claimed in claim 1, characterized in that thecapacitor (12) and the inductive element (11) are part of a measurementstructure, wherein the first winding (21) of the inductive element (11)interconnects the first and the second electrode (31,32) of thecapacitor (12), and the measurement structure further comprises a firstand a second transmission line, which lines are defined in the secondmetal film (6), are located substantially parallel to each other andperpendicular projections of the lines on the first metal film (3)overlap with the first winding (21).
 6. An electronic device (10,50) asclaimed in claim 1, characterized in that the capacitance density of thedielectric film (4) is at least ten times higher than that of theseparation layer (5).
 7. An electronic device (10,50) as claimed inclaim 6, characterized in that the first and second metal film (3,6)each have a thickness larger than 1 micron.
 8. A multilayer substratewith internal conductors provided with a measurement structure formeasurement of a dielectric constant of a dielectric comprising: acapacitor (12) having a first and a second electrode (31,32) and theintermediate dielectric (33), an inductive element (11) having a firstwinding (21), wherein the first winding (21) interconnects the first andthe second electrode (31,32) of the capacitor (12); a first and a secondtransmission line, which lines are located parallel to each other andare capacitively and inductively coupled to the first winding (21) ofthe inductive element (11).
 9. A multilayer substrate as claimed inclaim 8, characterized in that the substrate is provided with a firstand a second metal film (3,6), the first metal film (3) comprising thefirst electrode (31) of the capacitor (12) and the first winding (21) ofthe inductive element (11), the second metal film comprising the secondelectrode (32) of the capacitor (12) and the transmission lines, thefirst and second metal film (3,6) being mutually separated through adielectric film (4) of dielectric material constituting the dielectric(33) of the capacitor and a separation layer (5) of dielectric materialbeing at least present between the first winding (21) of the inductiveelement (11) and the transmission lines.
 10. A method of testing anelectronic device comprising an insulating body with internal conductorsand layers of dielectric material, the device being designed to operateat frequencies of more than 100 MHz, which method including thedetermination of a dielectric property of a layer of dielectric materialwith a measurement structure, characterized in that the device (10)according to claim 9 is tested and its measurement structure is used tomeasure the resonance frequency, which is converted to the dielectricproperty such as dielectric constant and dielectric loss, of thedielectric film (4) by comparison to a reference value.